Control for Torque Converter Having Multiple Selectively Engageable Converter Couplers

ABSTRACT

An apparatus and method of controlling a torque transmitting apparatus having multiple selectively engageable couplers is provided. The multiple couplers may be selectively engaged and disengaged to provide a mechanical, friction or fluid coupling between portions of the torque transmitting apparatus and other components of a vehicle powertrain during various operational stages. The control apparatus includes a fluid pressure control device and a fluid flow control device.

CROSS REFERENCE

This application is a continuation of and claims priority to U.S.Utility patent application Ser. No. 12/400,907, filed Mar. 10, 2009, nowprojected U.S. Pat. No. 8,527,169, and claims the benefit of andpriority to U.S. Provisional Patent Application No. 61/045,141, filedApr. 15, 2008, which is incorporated herein by this reference in itsentirety.

TECHNICAL FIELD

The present invention relates generally to control systems for motorvehicles equipped with automatic transmissions, and more particularly,to methods and systems for controlling operation of a torquetransferring apparatus having more than one selectively engageabledevice for coupling portions of the torque transferring apparatus toother components of the vehicle powertrain.

BACKGROUND

In a vehicle with an automatic transmission, a torque transferringapparatus is used to transfer torque from a drive unit, such as thevehicle engine, to the vehicle transmission. The torque transferringapparatus is typically interposed between the drive unit and thetransmission. Fluid couplings, such as torque converters, are widelyemployed for this purpose.

The typical torque converter has a torque input member (commonlydesignated as the pump or impeller) and a torque output member (commonlydesignated as the turbine). A reaction member (commonly designated asthe stator) may be interposed between the pump and the turbine to effecta more favorable direction for the flow of hydraulic fluid exiting theturbine and returning to the torque converter pump.

Hydraulic fluid is supplied to the torque converter under pressure by afluid supply and valve arrangement. Dynamic circulation of the hydraulicfluid through the torque converter effects rotation of the turbine inresponse to rotation of the torque converter pump.

Typically, the torque converter pump is coupled to the crankshaft of thevehicle engine, while the turbine is connected to an output shaft whichexits the torque converter to serve as the input shaft of the vehicletransmission gear assembly.

When a vehicle is not moving, and while the engine is idling (such aswhen the driver applies the brake, or the transmission is in neutral orpark), the torque converter pump is generally not spinning at asufficient angular velocity to supply the energy necessary to overcomethe static inertia of the vehicle. In this situation, the hydraulicfluid simply flows through the turbine, and ideally the turbine does notrotate. This allows the vehicle to remain at rest, even if thetransmission has been shifted into a selected drive range (i.e., aforward gear or reverse) and the engine is running.

As a request for vehicle movement is received (such as when the driverreleases the brake, applies the accelerator pedal, or shifts into aforward gear), the rotational speed of the engine, and therefore therotational speed of the torque converter pump, increases. At somerotational speed of the engine, sufficient energy is imparted to theturbine so that it overcomes the static inertia that had previouslyprevented the vehicle from moving. At that time, the energy transferredfrom the torque converter pump to the turbine is delivered to the drivewheels through the transmission.

Fluid exits the turbine and reenters the torque converter pump withoutany redirection, unless an intermediary such as a stator is interposedin the path which the hydraulic fluid follows between its exit from theturbine and its re-entry into the pump. The stator redirects thehydraulic fluid which has exited the turbine so that the fluid willenter the input of the pump in a direction that will cause the fluid toassist the engine in turning the pump. The force imparted by thereturning hydraulic fluid to the pump comprises an additional source ofkinetic energy. This additional energy applied to the pump results in anincrease in the force applied to drive the turbine, providing torquemultiplication.

In operation, torque converters require a source of pressurizedhydraulic fluid. The hydraulic fluid is generally drawn from thetransmission pan or from a sump, and delivered to the torque converterat a predetermined pressure. A valve controls the pressure of thehydraulic fluid supplied to the torque converter. The pressurizedhydraulic fluid is supplied to the torque converter, where it is used toeffect a hydraulic torque transfer between the pump and the turbinewithin the torque converter. Thereafter, the fluid is directed through acooling system to the fluid supply and then recycled.

Torque converter control valves usually permit fluid flow to the torqueconverter after the pressure at the outlet of the fluid supply reaches apredetermined value. As the pressure continues to increase, the torqueconverter valve directs excess fluid to the inlet side of the pump.

Torque converters are often provided with a clutch assembly thateffectively locks the torque converter pump and the turbine into aunitary rotating mass under certain operating conditions, for example,when “slip” (i.e., a difference in rotational speed) between the pumpand the turbine is not required. Typically, the torque converter clutchor “lockup” clutch is activated to effect unitary rotation of the torqueconverter pump and turbine in response to reduced hydraulic pressurewithin the torque converter.

The torque converter clutch assembly may also include a pump clutch,which is operable to disconnect the torque converter pump from thevehicle drive unit. This may be desirable when the vehicle is idling,for example. Embodiments of a torque converter having a clutch assemblyincluding a torque converter clutch and a pump clutch are described inHemphill et al., U.S. Patent Application Publication No. US2007-0074943.

SUMMARY

In one aspect of the present invention, a control for a torque converteris provided. The control is directed to a torque converter havingmultiple selectively and independently engageable clutches. The controlincludes a valve and fluid passage assembly operably couplable to thetorque converter to control the engagement and disengagement of theclutches during phases of operation of the torque converter. The valveand fluid passage assembly includes at least one multiplexed pressurecontrol valve. In other words, according to at least one embodiment, thenumber of pressure control valves in the valve and fluid passageassembly is less than the number of clutches of the torque converter.

The control may include a fluid flow control valve in fluidcommunication with the pressure control valve. The fluid flow controlvalve may include a first fluid chamber to selectively communicate witha first clutch of the torque converter, a second fluid chamber toselectively communicate with a second clutch of the torque converter,and a third fluid chamber to selectively communicate with one of thefirst and second clutches.

The fluid flow control valve has a first position and a second position.When the fluid flow control valve is in the first position, the thirdfluid chamber may be in fluid communication with the first clutch, andwhen the fluid flow control valve is in the second position, the thirdfluid chamber may be in fluid communication with the second clutch. Whenthe third fluid chamber is in fluid communication with the first clutch,the first fluid chamber may be in fluid communication with the secondclutch. When the third fluid chamber is in communication with the secondclutch, the second fluid chamber may be in fluid communication with thefirst clutch.

The control may also include an actuator coupled to the fluid flowcontrol valve to change the position of the fluid flow control valve,and an electrical control unit to send electrical signals to theactuator to change the position of the fluid flow control valve.

According to another aspect of the present invention, a control for atorque converter having multiple selectively and independentlyengageable clutches is provided. The control includes a valve systemoperably couplable to the torque converter to control the engagement,trimming, and disengagement of each of the clutches during differentphases of operation of the torque converter.

The valve system may include a trim valve and a logic valve in fluidcommunication with the trim valve. Further, the valve system may includemultiple fluid passages to connect the torque converter clutches to thelogic valve, and one fluid passage connecting the trim valve and thelogic valve. The valve and fluid passage assembly may be incorporatedinto an electro-hydraulic control system for a vehicle transmission.

In another aspect of the present invention, a control for a torquetransferring apparatus of a vehicle is provided, including an actuatorand a flow control device. The actuator has a first actuator state and asecond actuator state. The flow control device has a first device stateand a second device state. The flow control device is in fluidcommunication with the actuator, such that when the actuator is in thefirst actuator state and the flow control device is in the first devicestate, the actuator and the flow control device are in fluidcommunication with a first coupler of a torque transferring apparatusoperable to transfer torque from a drive unit of a vehicle to a drivenunit of the vehicle.

The first coupler is coupled to a first portion of the torquetransferring apparatus and is selectively couplable to a portion of thedrive unit of the vehicle. The drive unit provides torsional input tothe first portion of the torque transferring apparatus. When theactuator is in the second actuator state and the flow control device isin the second device state, the actuator and the flow control device arein fluid communication with a second coupler of the torque transferringapparatus.

The second coupler is coupled to a second portion of the torquetransferring apparatus spaced from the first portion of the torquetransferring apparatus. The second portion of the torque transferringapparatus provides torsional output to the driven unit of the vehicle.Also, the second coupler is selectively couplable to the first portionof the torque transferring apparatus.

The control may also include a pressure control device in fluidcommunication with the flow control device. According to one embodiment,the actuator is “off” in the first actuator state, and the actuator is“on” in the second actuator state. Further, in one embodiment, the flowcontrol device is a flow valve and the flow valve is in a spring setposition in the first device state, and the flow valve is in a pressureset position in the second device state. In certain embodiments, thefirst coupler is a pump clutch and the second coupler is a torqueconverter or lockup clutch.

According to one embodiment, when the flow control device is in thefirst device position, the second coupler is disengaged, and when theflow control device is in the second device position, the first coupleris engaged.

In yet another aspect of the present invention, a control for a torquetransferring apparatus is provided, including a fluid supply, a controlassembly, and electrical circuitry. The control is directed to a torquetransferring apparatus which transfers torque from a drive unit of amotor vehicle to a driven unit of the motor vehicle. The controlassembly is operably coupled to the fluid supply, and includes a fluidpressure control apparatus and a fluid flow control apparatus in fluidcommunication with the fluid pressure control apparatus. The electricalcircuitry is operably coupled to the control assembly.

The control cause a first coupler of a torque transmitting apparatus toselectively engage and disengage from an output member of a vehicledrive unit and causes a second coupler of the torque transmittingapparatus to selectively engage and disengage from a first portion ofthe torque transmitting apparatus.

The fluid pressure control apparatus may include a trim valve and thefluid flow control apparatus may include a flow valve having a firststate and a second state. An actuator may be provided to selectivelychange the state of the flow valve from the first state to the secondstate. In at least one embodiment, the controller sends at least oneelectrical signal to the actuator to change the state of the flow valve.The flow valve may control the first coupler when the flow valve is inthe first state and may control the second coupler when the flow valveis in the second state.

According to a further aspect of the present invention, a control for atorque transferring apparatus of a vehicle is provided, including anelectrical control apparatus and a tangible medium including executableprogramming instructions. The electrical control apparatus receivessignals indicative of the operational state of a vehicle and executesexecutable instructions to control operation of the torque transferringapparatus. The tangible medium is accessible by the electrical controlapparatus. The executable instructions include logic to determine anoperational state of a vehicle having a drive unit, a transmission, anda torque transferring apparatus, which transfers torque from the driveunit to the transmission. The logic is adapted for a torque transferringapparatus having a first coupler and a second coupler, where the firstcoupler is coupled to a first portion of the torque transferringapparatus and is selectively couplable to an output member of thevehicle drive unit; while the second coupler is coupled to a secondportion of the torque transferring apparatus and is selectivelycouplable to the first portion of the torque transferring apparatus.

The instructions also include logic to selectively change a state of atorque transferring apparatus control assembly from a first state to asecond state in response to a change in the operational state of thevehicle. In at least one embodiment, the torque transferring apparatuscontrol assembly includes at least one electro-hydraulic apparatus. Theprocess of selectively changing a state of the torque transferringapparatus control assembly includes selectively applying electricalcurrent to a portion of the electro-hydraulic apparatus.

Also in certain embodiments, the torque transferring apparatus controlassembly selectively alters fluid pressure in at least a portion of theelectro-hydraulic apparatus based on the operational state of thevehicle and also selectively alters a path of fluid flow in at least aportion of the electro-hydraulic apparatus based on the operationalstate of the vehicle. In one or more embodiments, at least theelectrical control apparatus is incorporated in a transmission controlmodule of the vehicle.

Patentable subject matter may include one or more features orcombinations of features shown or described anywhere in this disclosureincluding the written description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description refers to the following figures in which:

FIG. 1 is a block diagram representing a portion of a vehicle powertrainincluding a drive unit, a transmission, a torque transferring apparatus,a plurality of coupling devices coupled to the torque converter, and acontrol assembly coupled to the coupling devices;

FIG. 2 is a schematic of a portion of one embodiment of the controlassembly of FIG. 1, illustrating fluid flow and fluid pressures when thetorque transferring apparatus is operating in a first stage;

FIG. 3 is a partial schematic of the control assembly of FIG. 2,illustrating fluid flow and fluid pressures when the torque transferringapparatus is operating in a second stage;

FIG. 4 is a partial schematic of the control assembly of FIG. 2,illustrating fluid flow and fluid pressures when the torque transferringapparatus is operating in a third stage;

FIG. 5 is a partial schematic of the control assembly of FIG. 2,illustrating fluid flow and fluid pressures when the torque transferringapparatus is operating in a fourth stage;

FIG. 6 is a partial schematic of the control assembly of FIG. 2,illustrating fluid flow and fluid pressures when the torque transferringapparatus is operating in a fifth stage;

FIG. 7 is a graph illustrating changes in pressure in different portionsof the torque transferring apparatus through various stages ofoperation, according to the embodiment of the control assembly shown inFIGS. 2-6;

FIG. 8 is a table indicating the status of different components of thetorque transferring apparatus and control assembly through the variousstages of operation; and

FIG. 9 is a flow diagram illustrating computer-executable operations ofa control for a torque transferring apparatus according to the presentinvention.

In general, like structural elements on different figures refer toidentical or functionally similar structural elements although referencenumbers may be omitted from certain views of the drawings forsimplicity.

DETAILED DESCRIPTION

Aspects of the present invention are described with reference to certainillustrative embodiments shown in the accompanying drawings anddescribed herein. While the present invention is described withreference to the illustrative embodiments, it should be understood thatthe present invention as claimed is not limited to the disclosedembodiments.

Motor vehicles typically have several different modes or phases ofoperation, including idle, launch, torque conversion, and “lockup”modes. Motor vehicles also often experience a variety of differentevents and conditions during operation, relating to terrain,temperature, driver preferences, traffic conditions, and/or otherfactors. The vehicle transmission is often expected to respond to theseconditions and events to cause the vehicle speed to adjust appropriatelyand in a smooth and efficient manner.

In torque converters that are equipped with multiple clutches or similarcouplers, such as the arrangements disclosed in U.S. Patent ApplicationPublication 2007/0074943 to Hemphill, et al. (“Hemphill”), the multipletorque converter couplers may be selectively engaged and disengaged toprovide greater engine efficiency and/or smoother transitions as thevehicle operates in different phases or encounters different operatingconditions or events.

For example, during the idle phase, both the pump clutch and the torqueconverter or lockup clutch of a torque converter having a dual clutcharrangement may be disengaged. During the launch and torque converterphases, the pump clutch may be engaged while the lockup clutch remainsdisengaged. During the lockup phase, both the pump clutch and the lockupclutch may be engaged.

Hemphill discloses several embodiments of torque converters havingmultiple clutches or similar devices, as well as fluid chambers withinthe torque converter for receiving pressurized fluid to controloperation of the clutches. Hemphill mentions that valves are used tocontrol pressure in the fluid chambers of the torque converter. However,Hemphill does not disclose any structure other than the torque converterarrangement itself. In particular, Hemphill does not disclose any valvecontrol assembly for controlling the multiple-clutch torque converter.

Simplified and sophisticated control of the torque converter clutches orcouplers can be achieved with a valve assembly operably coupled to oneor more electrical controls, as disclosed herein. Interfacing of thetorque converter clutch control with a transmission control assemblyexpands the range of possible inputs to the torque converter clutchcontrol to include transmission control parameters, such as transmissioninput speed, transmission output speed, turbine speed, driver-requestedtorque, and engine output torque, to name a few, thereby additionallyenabling a finer degree of control of the torque converter and itsclutches or couplers.

For instance, closed-loop control methods including but not limited tothose known as reduced engine load at stop (“RELS”), variable K factorcontrol, and electronic converter clutch control (“ECCC”), may beapplied to multiple-clutch arrangement torque converters such asHemphill's, through application of aspects of the present invention.

In idle mode, when the vehicle is turned on but in a stopped position,it is desirable for little or no torque to be transferred to the drivewheels while the engine is running. Mechanical decoupling of the vehicletransmission from the drive unit during the stopping and/or idlingphases can be provided by disengagement of a torque converter pumpclutch and disengagement of a torque converter lockup clutch, to reducethe load on the vehicle drive unit, thereby improving engine efficiencyand fuel economy. Aspects of the present invention provide a “reducedengine load at stop” method for releasing the pump clutch during theidle phase, while the torque converter clutch is also released and arelatively constant pressure is maintained in the torus cavity of thetorque converter, as further described below.

As a request for motion is received, the vehicle transitions to thecreep or launch phase. During the launch phase, engine speed typicallyincreases to begin to cause torque to be transferred to the vehicledrive wheels through the torque converter and transmission gearassembly. Often, a lower gear ratio is desired during the launch phaseto achieve a smoother and/or faster transition. During the launch phase,aspects of the present invention provide a method of variable k factortrimming of the pump clutch to control the application or engagement ofthe pump clutch, as further described below with reference to theillustrative embodiment.

During the normal torque converter phase, shifts to higher gears mayoccur. The transmission input speed (i.e. torque converter pump speed)and the turbine speed are still normally greater than the actual vehiclespeed, and the torque converter pump speed is greater than the turbinespeed. Torque multiplication is typically provided during the launch andtorque converter phases. During these phases, aspects of the presentinvention maintain the engagement of the pump clutch while maintainingthe disengagement of the lockup clutch and maintaining a relativelyconstant pressure in the torus cavity of the torque converter.

Aspects of the present invention provide a “torque converter clutchtrim” phase or “TCC trim” phase, as shown in FIG. 7, described below.During the TCC trim phase, the lockup clutch is trimmed to provide agreater degree of control over the application and release of the lockupclutch while at the same time maintaining engagement of the pump clutchand managing the fluid pressure in the torus cavity of the torqueconverter.

A trim phase generally allows smoother engagement or disengagement ofthe clutch or coupler by providing a steady increase or decrease influid pressure. A steady, predictable increase or decrease in pressureas a clutch is being applied or released may be desirable for improvedshift quality or for other reasons.

During the lockup mode, the torque converter pump and the turbine aregenerally spinning at the same speed. To improve engine efficiencyduring this phase, it is often desirable to mechanically couple thetorque converter pump and the turbine to reduce inefficiencies resultingfrom the fluid flow through the torque converter. A torque converterclutch or lockup clutch is often provided for this purpose. During thelockup phase, aspects of the present invention provide known closed loopelectronic converter clutch control methods (“ECCC”) to manageapplication or engagement of the lockup clutch.

Also during the TCC trim and lockup phases, aspects of the presentinvention provide a knockdown feature on the main regulator valve,wherein pressure is reduced at the main regulator valve.

In general, the controls and methods of the present invention providethat the pump clutch is disengaged in the idle phase, trimmed in thelaunch phase, and engaged through the converter, TCC trim and lockupphases; while the lockup clutch generally remains disengaged through theidle, launch and converter phases, is trimmed in the converter clutchcontrol phase, and is engaged in the lockup phase, as shown by the tableof FIG. 8.

FIG. 1 depicts a simplified block diagram of a vehicle powertrain 10,including a drive unit 12, a torque transferring apparatus 14, atransmission assembly 16, and a vehicle load 18. Drive unit 12 generallyprovides a torque output to torque transferring apparatus 14 via anoutput shaft 13. Drive unit 12 may be an internal combustion engine of acompression-ignition type (i.e. diesel) or a spark-ignition type (i.e.gasoline), an engine-electric motor combination, or the like. Torquetransferring apparatus 14 generally converts and/or transfers the torqueoutput from drive unit 12 to the vehicle transmission assembly 16 viaturbine shaft or transmission input shaft 17. As such, torquetransferring apparatus 14 normally includes a fluid coupling such as atorque converter.

Transmission assembly 16 includes the assembly of gears and clutchesthat are selectively engaged and disengaged by electro-hydraulictransmission control 34 to cause the vehicle to move at varying speeds.As such, elements of transmission 16 are in fluid communication withelements of control 34 via one or more conduits or passages 46. Anexample of a suitable transmission assembly is a six-speed planetarygear arrangement, such as shown in U.S. Pat. No. 4,070,927 to Polak. Oneexample of a suitable transmission control for a six-speed transmissionis disclosed in U.S. Patent Application Publication No. 2003/0114261 toMoorman, et al. Another example of an electro-hydraulic transmissioncontrol system is disclosed in U.S. Pat. No. 5,601,506 to Long, et al.

The present invention may be applied to these and other types oftransmission systems, including but not limited to eight-speed automatictransmission systems, as shown in U.S. Provisional Patent ApplicationNo. 61/045,141, which is incorporated herein by this reference. Includedin such provisional application are diagrams of a manual valveelectro-hydraulic control assembly for an eight-speed transmissionsystem and a fly-by-wire electro-hydraulic control assembly for aneight-speed transmission system. These diagrams show converter controlssuch as control 30, 31, including a multiplexed trim system and aconverter flow valve such as valve 130, incorporated into the controlassembly for the manual system and the control assembly for thefly-by-wire system.

Transmission 16 drives the vehicle load 18 via transmission output shaft19. Vehicle load 18 generally includes the drive wheels and driven loadmass. The actual weight of vehicle load 18 may be quite considerableand/or vary considerably over the course of the vehicle's use, as may bethe case with commercial vehicles such as trucks, buses, emergencyvehicles, and the like.

Torque transferring apparatus 14 includes a plurality of selectivelyengageable and disengageable couplers 20, 22 configured to alter thecoupling (or lack thereof) between drive unit 12 and transmission 16.Couplers 20, 22 are generally configured to selectively achieve amechanical, fluid or friction coupling between components of thedrivetrain 10 in response to various conditions or changes inconditions. For instance, couplers 20, 22 may be torque transmittingdevices or friction devices. Couplers 20, 22 may be fluid-operateddevices such as clutch- or brake-type devices. As such, couplers 20, 22may be stationary- or rotating-type devices. Couplers 20, 22 may betorque converter clutches or similar functioning devices, pump clutchesor similar functioning devices, or a combination thereof.

In general, couplers 20, 22 can be operated independently of each other.For instance, couplers 20, 22 may be simultaneously engaged,simultaneously disengaged, or one of couplers 20, 22 may be engagedwhile the other is disengaged.

Couplers 20, 22 may be couplable to respective portions of powertrain 10by various means, including being splined to a piston and/or connectedto a clutch plate. A friction material may be applied to one or moreportions of couplers 20, 22 to facilitate engagement or for otherreasons.

Couplers 20, 22 are in fluid communication with torque transferringapparatus (TTA) control 30 via one or more lines or conduits 24, 28.Control 30 includes electro-hydraulic controls configured to selectivelyengage and disengage couplers 20, 22 from other elements of thepowertrain 10. For instance, coupler 20 may be configured to couple aportion of the torque transferring apparatus 14 to a portion of thedrive unit 12, while coupler 22 may be configured to couple portions ofthe torque transferring apparatus 14 together.

Control 30 includes an electro-hydraulic valve assembly configured toselectively control the application, trimming, and release of couplers20, 22. For example, control 30 may adjust a path of fluid flow and/oradjust pressure of fluid in one or more of the lines 24, 28 to engageand disengage couplers 20, 22 or for other reasons.

While shown as separate elements in FIG. 1, controls 30 and 34 may bepart of one electro-hydraulic control assembly. Controls 30 and 34 arein fluid communication with a fluid supply 40 and in electricalcommunication with an electronic or electrical control unit 32. Fluidsupply 40 supplies a pressurized fluidic medium such as hydraulic oil orthe like to electro-hydraulic controls 30, 34 through one or more fluidpassages or conduits 42, 44. In general, fluid supply 40 includes afluid reservoir or sump, a pump (such as a hydraulic positivedisplacement pump, variable displacement pump, or electricallycontrolled hydraulic pump) for drawing fluid out of the reservoir, aregulator valve for establishing a regulated pressure or main pressurein fluid passages 42, 44, and fluid passages providing fluidcommunication among the reservoir, pump, valving and fluid lines. Adescription of an exemplary regulator valve assembly for a torqueconverter can be found in U.S. Pat. No. 5,319,949 to Long et al.

Electronic control 32 controls the electro-hydraulic controls 30, 34based on one or more electrical inputs 48, 50, 52, 54, and 56. Suchinputs may be received from one or more components of the transmission16, torque transferring apparatus 14, drive unit 12, or other componentsof the vehicle. Such inputs may include electrical or analog signalsreceived from sensors, controls or other like devices associated withthe vehicle components. For instance, inputs 48, 50, 52, 54, 56 mayinclude signals indicative of transmission input speed, driver requestedtorque, engine output torque, engine speed, temperature of the hydraulicfluid, transmission output speed, turbine speed, brake position, gearratio, torque converter slip, and/or other measurable parameters.

Electrical control 32 generally includes electrical circuitry configuredto process, analyze or evaluate one or more of inputs 48, 50, 52, 54, 56and issue electrical control signals to controls 30, 34 as neededthrough one or more electrical lines or conductors 36, 38. Connections36, 38 may include hard-wired and/or networked components in anysuitable configuration including, for example, insulated wiring and/orwireless transmission as may be appropriate or desired.

Electrical circuitry of control 32 includes computer circuitry such asone or more microprocessors and related elements configured to processexecutable instructions expressed in computer programming code or logic,which is stored in one or more tangible media, i.e., any suitable formof memory or storage media that is accessible or readable by theprocessor or processors. Such instructions include commands toselectively alter or adjust the path of fluid flow and/or the fluidpressure in the one or more lines 24, 28 as needed or desired to controlthe operation of couplers 20, 22. An example of such computer-executablelogic is illustrated in FIG. 9, described below. Control 32 may alsoinclude analog to digital converters and/or other signal processingcircuitry or devices as needed to process one or more of the inputs 48,50, 52, 54, 56.

While shown schematically as a single block 32, it will be understood bythose skilled in the art that portions of control 32 may be implementedas separate logical or physical structures. For example, electroniccontrols for transmission 16 may be physically and/or logicallyseparated from electronic controls for the torque transferring apparatuscouplers 20, 22.

One embodiment 31 of an electro-hydraulic control assembly 30, forcontrolling a plurality of couplers 21, 23 of a torque transferringapparatus 15, is shown in FIGS. 2-6. In FIG. 2, control 31 is showncoupled to an exemplary torque transferring apparatus 15; however,control 31 is adaptable for use with other similar devices having morethan one coupler such as couplers 21, 23.

Torque transferring apparatus 15 is a torque converter having amultiple-clutch arrangement, such as those described in U.S. PatentApplication Publication No. 2007/0074943 to Hemphill et al. Torqueconverter 15 includes a torque converter pump 2, a torus cavity 3, aturbine 6, a stator 8, a lockup or torque converter clutch 23 and a pumpclutch 21. Torque transferring apparatus also includes a damper 4, whichmay be coupled to pump clutch 21 and lockup clutch 23 as described inHemphill et al. Examples of a suitable damper are disclosed in U.S. Pat.No. 6,494,303 to Reik et al.

Fluid passages 25, 27, and 29 provide fluid communication between pumpclutch 21 and control 31, torus cavity 3 and control 31, and lockupclutch 23 and control 31, respectively.

Control 31 includes a pressure control apparatus 60, 80 and a flowcontrol apparatus 130,180. In the illustrative embodiment, pressurecontrol device 80 is a regulator valve or trim valve, or similarmechanism for varying pressure in the fluid lines 25, 27, 29. Flowcontrol device 130 is a converter flow valve, i.e., a logic valve orrelay valve or similar mechanism configured to alter the path of fluidflow from device 80 to fluid lines 25, 27, 29. In this valveconfiguration, pressure control device 80 is multiplexed to control bothof the couplers 21, 23 in the multiple coupler arrangement of the torquetransferring apparatus 15. More particularly, in the illustrativeembodiment, a single trim valve 80 is used to control operation of bothpump clutch 21 and lockup clutch 23.

Pressure control device 80 and flow control device 130 are actuated byactuators 60, 180, respectively. Actuators 60, 180 are in electroniccommunication with electronic control unit or electrical circuitry 35,which operates in a similar manner to electronic control 32 describedabove. In the illustrative embodiment, control 35 is implemented as partof a transmission control module or TCM, which is installed in thevehicle.

Actuator 60 may be a variable bleed solenoid valve, a pulse widthmodulated solenoid valve, a force motor, or similar mechanism configuredto vary the force or pressure applied to the trim valve head 118. In theillustrative embodiment, actuator 60 is a normally low (zerocurrent=zero pressure) variable bleed solenoid valve including asolenoid 58. Fluid enters valve 60 through control pressure inlet 68, ata predetermined control pressure set by a regulator valve of a fluidsupply similar to fluid supply apparatus 40 described above. In theillustrative embodiment, the control pressure is in the range of about110 psi.

Fluid may exit valve 60 through exhaust outlet 66. How restrictors ororifices 67, 69 are configured to regulate the rate or volume of fluidflowing through valve 60 to thereby regulate the fluid pressure appliedto the head of valve 80. As such, the pressure applied to valve 80depends on the configuration of valve 60, including the size orconfiguration of orifices 67, 69.

Orifice 67 has a variable-sized opening that is adjusted by solenoid 58,such that when no electrical current is flowing to solenoid 58 throughline 37, orifice 67 is wide open, allowing fluid to flow to exhaust 66.As electrical current is applied to solenoid 58 through line 37, orifice67 begins to close or become smaller, thereby restricting flow toexhaust 66 and allowing fluid pressure to increase in inlet 70 of trimvalve 80. Another restrictor or orifice 64 is provided in inlet line 70to add pressure stability between solenoid 58 and the valve head 118.This allows stepping down the control pressure during the trim phase ofcontrol 31 described below with reference to FIG. 3.

Valve 80 is situated in a more or less cylindrical valve chamber of ahousing, which is not shown for simplicity. A plurality of fluid portsextend through the housing into the valve chamber at spaced apartlocations. Valve 80 is longitudinally translatable within the valvechamber to provide varying degrees of communication with lines 25, 29through the fluid ports over the range of operating modes of the torqueconverter 15.

Valve 80 includes a valve head 118, and a longitudinal spool member 81.Spool member 81 has a plurality of spool subsections 86, 88 separated bylands 82, 84. Lands 82, 84 extend radially outwardly from the spoolmember 81. As such, lands 82, 84 have a greater area than spool members86, 88, respectively. Lands 82, 84, spool members 86, 88 and theinterior wall of the valve chamber cooperate to define subchambers 85,120 within the valve chamber. Subchamber 120 is defined by area 112 ofland 82, area 100 of land 84, and the diameter of spool member 86.Subchamber 85 is defined by area 98 of land 84, the diameter of spoolmember 88 and area 128 of spool member 88. A spring 122 is provided insubchamber 85, which counteracts pressure applied to valve head 118.

In general, the fluid pressure applied to valve head 118 times area 110equals the pressure in line 106 times area 128 plus the bias of spring122. Area 110 is greater than area 128. When the output pressure in line106 is less than the input pressure applied to head 118, spool 81 isdriven down in the valve chamber, opening passage 94, 120. Pressure inthe output passage 106 subsequently begins to increase after passage 94,120 is opened, urging spool 81 upward in the valve chamber. Thus, valve80 alternates between the up and down positions in real time.

References to an “area” of a land or spool member defining a portion ofa valve subchamber generally relate to a calculation of the area of thesurface of the respective land or spool member interfacing with fluid inthe valve (i.e., for a circular surface, pi times the radius of thecircle squared). Chamber 96 is normally exhausted.

In the first phase of torque converter operation, which is the idle orstop phase, control 31 is configured as shown in FIG. 2. Valve 60 isenergized by electrical current received from control unit 35, such thatcontrol pressure flows through passage 70 to the valve head 118. Thepressure applied to valve head 118 forces valve 80 to translatelongitudinally downwardly in the valve chamber, compressing spring 122.Downward translation of valve 80 opens fluid passage 120 to connect withmain pressure line 94 and feed passage 33.

Valve 130 is a converter flow valve actuated by a solenoid valve 180.Solenoid valve 180 is a normally low, on/off solenoid valve or similarsuitable actuator. During the first phase of torque converter operation,valve 180 is de-energized or “off.” As such, fluid in line 194 isexhausted through passage 190. During phase I, valve 130 is in thespring set position. In general, the exhaust pressure is in the range ofabout 0 pounds per square inch (psi).

Valve 180 remains off, and thus valve 130 remains in the spring setposition, during the idle, launch, and normal converter operationphases, i.e. phases I, II, and III as shown in FIG. 8. As such, duringthese phases, feed passage 33 communicates with pump clutch feed passage25 through subchamber 166 of valve 130.

During phase I, the pressure in main line 94 is the main pressurecontrolled by the main regulator valve of the fluid supply discussedabove. In the illustrative embodiment, the main pressure is in the rangeof about 50-250 psi. As such, maximum fluid pressure is applied to pumpclutch 21 during the first stage of torque converter operation. In theillustrative embodiment, when maximum pressure is applied to pump clutch21, pump clutch 21 is released or disengaged from the torque converterhousing or is otherwise disengaged from the drive unit of the vehicle.

During phases I, II, and III, i.e., during the idle, launch, and normalconverter operation stages, fluid from overage reservoir 104 flows totorus cavity 3 and is maintained at a converter in pressure in the rangeof about 100 psi. Also during these phases, fluid from converter outpassage 27 flows to cooler in passage 102 and is maintained at apressure in the range of about 50 psi.

During stage II of torque converter operation, i.e., during the launchphase, shown by FIG. 3, fluid pressure in pump cavity and pump feed 25,33 is gradually decreasing as fluid pressure applied to trim valve head118 is being trimmed as a result of decreasing current being provided toactuator 60. As the electrical current decreases, restrictor 67 beginsto open, allowing fluid to flow to exhaust 66. In the illustrativeembodiment, the trim pressure varies in the range of about 0-110 psi.

As pressure applied to valve head 118 decreases, spring 122 forces spoolmember 81 to translate upwardly in the valve chamber. As valve 80translates upwardly in the direction of arrow 116, fluid passage 33 isdisconnected from main line 94 by the interposition of land 84 therein.As a result, passage 33 is in communication with subchamber 120 of valve80, subchamber 166 of valve 130 and pump feed passage 25, at the trimpressure. Passage 27 remains in communication with torus cavity 3,subchamber 164 of valve 130, and header 102. Passage 29 remains incommunication with lockup cavity 23, subchamber 164 of valve 130, andheader 104. Valve 130 remains in the spring set position, as actuator180 remains in the off position in stage II.

During stage III of torque converter operation, i.e., during the normalconverter operation (torque multiplication) phase, shown by FIG. 4,actuator 60 is de-energized and fluid pressure in the pump cavity 21 andlines 25, 33 is at a minimum (exhaust pressure or about 0 psi). Valve 80is fully biased in the upward position in the valve chamber by spring122. Valve head 118 and area 110 of land 82 are now interposed in fluidpassage 70 such that no pressure is applied to valve head 118 frompassage 70 in stage III. Subchamber 120 of valve 80 is in fluidcommunication with exhaust port 92, line 33, subchamber 166 of valve130, and pump feed passage 25 at the exhaust pressure. Passage 27remains in communication with torus cavity 3, subchamber 162 of valve130, and header 102, and passage 29 remains in communication with lockupcavity 23, subchamber 164 of valve 130, and header 104, as describedabove.

Valve 130 remains in the spring set position, as actuator 180 remains inthe off position, in stage III. With the fluid pressure in the pumpcavity at a minimum, the pump clutch 21 is applied to engage the torqueconverter 15 with the vehicle drive unit. In the illustrativeembodiment, the pressure in the pump cavity and thus in line 25 remainsat a minimum, and thus the pump clutch 21 remains applied, during thesubsequent phases IV and V of torque converter operation as shown by thegraph of FIG. 7 and indicated in the table of FIG. 8.

During the fourth stage of torque converter operation, referred toherein as the “TCC trim” phase, the lockup clutch 23 is being trimmedwhile the pump clutch 21 remains engaged. Actuator 180 is energized byan electrical signal from control unit 35 over via line 39. Activationof valve 180 results in valve 130 translating upwardly in the directionof arrow 126, into the pressure set position, as control pressure isallowed to flow to the valve head 142 as shown in FIG. 5. When valve 130is in the pressure set position, fluid flow is redirected and flows tolockup clutch feed 29 instead of pump clutch feed 25.

Valve 130 is a converter flow valve, also known as a logic valve orrelay valve. Valve 130 is situated in a more or less cylindrical valvechamber of a housing, which is not shown for simplicity. A plurality offluid ports extend through the housing into the valve chamber at spacedapart locations. Valve 130 is longitudinally translatable within thevalve chamber to provide varying degrees of communication with lines 25,27, and 29 through the fluid ports over the range of operating modes ofthe torque converter 15.

Valve 130 includes a valve head 142, and a longitudinal spool member161. Spool member 161 has a plurality of spool subsections 132, 134,136, 138, 140 separated by lands 144, 146, 148, 150, 152. Lands 144,146, 148, 150, 152 extend radially outwardly from the spool member 161.Lands 144, 146, 148, 150, 152, spool subsections 132, 134, 136, 138, 140and the interior wall of the valve chamber cooperate to definesubchambers 160, 162, 164, 166, 168, 170 within the valve chamber.Subchamber 160 is defined by area 143 of land 144 and the diameter ofspool member 132. Subchamber 162 is defined by area 145 of land 144, thediameter of spool member 134, and area 147 of land 146. Subchamber 164is defined by area 149 of land 146, the diameter of spool subsection136, and area 151 of land 148. Subchamber 166 is defined by area 153 ofland 148, the diameter of spool member 138, and area 155 of land 150.Subchamber 168 is defined by area 157 of land 150, the diameter of spoolmember 140, and area 163 of land 152. A portion of area 159 of land 152and valve head 142 is interposed in head chamber 170, which is in fluidcommunication with knockdown header 194 and actuator 180.

As mentioned above, actuator 180 is a solenoid valve or similar typeactuator coupled to transmission control module 35. In the illustrativeembodiment, actuator 180 includes a normally low, on-off solenoid 182and a spring 184. During the idle, launch and normal converteroperational stages of torque converter 15, actuator 180 is off,de-energized, or otherwise deactivated as indicated in the table of FIG.8. As such, during these phases, valve 130 is biased in the spring setor “down” position by spring 133 and valve head 142 and a portion ofland 152 are interposed in head chamber 170 during phases I, II and III.

In the spring set position of stages I-III, spring 133 is uncompressed.As such, during these stages, subchamber 162 is in fluid communicationwith coolant reservoir 102 and passage 27 at the lube pressure;subchamber 164 is in fluid communication with overage header 104 andlockup clutch feed passage 29 at the converter pressure; subchamber 166is in fluid communication with trim valve 80 via line 33 and is in fluidcommunication with pump clutch feed passage 25; subchamber 168 is influid communication with exhaust chamber 188; and chamber 170 is incommunication with knockdown header 194, as shown in FIGS. 2-4.

When actuator 180 is activated or energized, valve 130 is shifted to thepressure set or “up” position as shown in FIGS. 5-6. In the pressure setposition, fluid at the control pressure is applied to valve head 142through chamber 170, thereby compressing spring 133.

In the TCC trim stage or phase IV of the torque converter operation,shown by FIG. 5, the torque converter clutch or lockup clutch 23 istrimming, and the pressure in the lockup clutch cavity is graduallydecreasing as shown by the graph of FIG. 7. Whereas the fluid pressurein the lockup cavity and lockup feed passage 29 was previously at thenormal torque converter pressure, it is now at the trim pressure byvirtue of the coupling of trim valve 80 to lockup feed 29 by subchamber166. Trim valve 80 is in a similar state to FIG. 3, i.e., electricalcurrent at actuator 60 is being varied to adjust the fluid pressurebeing applied to valve head 118.

Also during phase IV, subchamber 162 of valve 130 is in fluidcommunication with main pressure line 94 and passage 27, therebyincreasing the fluid pressure in torus cavity 3 as shown by the graph ofFIG. 7. Subchamber 164 is in fluid communication with headers 102, 104.Subchamber 166 connects trim passage 33 with lockup passage 29 andsubchamber 168 connects pump feed 25 to exhaust 188.

During phase V, control 31 assumes the configuration shown in FIG. 6. Inthis phase, the lockup clutch or torque converter clutch 23 is appliedwhile the pump clutch 21 remains engaged. Logic valve 130 remains in thepressure set or “up” position, however, trim valve 80 is fullytranslated upwardly in the direction of arrow 124, causing subchamber120 to connect with exhaust header 92, thereby connecting lockup passage29 to exhaust via passage 33 and subchamber 166 of valve 130. Solenoid60 opens orifice 67 fully so that line 70 is exhausted to outlet 66.

With fluid pressure at a minimum in lockup clutch feed line 29, lockupclutch is engaged, thereby achieving a mechanical/frictional couplingbetween the torque converter 15 and the vehicle transmission. With boththe pump clutch and the torque converter clutch engaged, amechanical/frictional coupling is achieved from the vehicle drive unitthrough the torque converter to the transmission input shaft.

A graph illustrating the relative changes in fluid pressure in the pump,torus, and lockup cavities of torque converter 15 through the variousstages of operation I, II, III, IV and V, is shown in FIG. 7. Line 200represents the pressure in the pump cavity 21, 25, line 202 representsthe pressure in the lockup cavity 23, 29, and line 204 represents thepressure in the torus cavity 3. During the idle or stop phase I, fluidpressure in both the pump and lockup cavities is high. Pressure in thepump cavity 21, 25 decreases during the launch phase, according to avariable k factor method, for example, as the pump clutch 21 prepares toengage. Pressure in the pump cavity 21, 25 is at a minimum during thesubsequent phases II, IV and V, as the pump clutch 21 is engaged.

During the first three stages I, II, and III, fluid pressure in thelockup cavity 23,29 remains substantially constant. In stage IV, thefluid pressure in the lockup cavity 23, 29 is adjusted, according to anelectronic torque converter clutch control algorithm, for example, asthe lockup clutch 23 prepares to engage. Pressure in the lockup cavity23, 29 is at a minimum during the lockup phase V.

During the first three stages I, II, and III, fluid pressure in thetorus cavity 3 remains substantially constant. Pressure in the toruscavity 3 may be increased in stage IV to provide “knockdown” on the mainregulator valve when the lockup clutch 23 is applied. The knockdownfeature essentially reduces the fluid pressure at the main regulatorvalve of the main hydraulic fluid supply. The increased torus cavitypressure is maintained through stage V, as the lockup clutch 23 isapplied. However, control 31 maintains the torus cavity pressure belowthe main pressure to prevent ballooning of the torus cavity 3.

The states or settings of various components of torque converter 15 andcontrol 31 through the operational stages I, II, III, IV and V are shownin the table of FIG. 8 and discussed above. Stages I, II, III, IV and Vof FIG. 8 correspond to the stages I, II, III, IV and V of FIG. 7.

FIG. 9 illustrates an example of computer operations executable bycontrol unit 32, 35 to provide torque converter control 30, 31. Computerprogram 210 includes instructions for executing a first computer process212 of monitoring one or more vehicle state indicators. Vehicle stateindicators may include but are not limited to electrical signalsindicating a current status or condition of a component of the vehicle,which may be sensed or otherwise determined or estimated, such as enginespeed, vehicle speed, turbine speed, transmission gear ratio, fluidpressures, fluid temperatures, pump clutch status, torque converterclutch status, brake position, torque converter slip, and others. One ormore of the vehicle state indicators are analyzed or evaluated byprocess 212, to determine the current stage of vehicle or torqueconverter operation, for example.

A decisional process 214 determines whether it is necessary to controlone or another of the multiple torque converter couplers or clutches,based on the one or more of the vehicle parameters. As described above,in the illustrative embodiment, the converter flow valve and itsactuator determine whether the pump clutch or the lockup clutch is beingcontrolled. Thus, at decisional block 214, if the vehicle is in one ofstages I, II or III (i.e., idle, lockup, or normal converter operation),or if analysis of some other vehicle parameter indicates that a firstcoupler needs to be controlled, then at functional block 216 the firstactuator will be set to a first state such that the first coupler willbe controlled by the trim system. For example, in the illustrativeembodiment, if the vehicle is in stage I, II or III, then valve 180 willbe deactivated or set to the off position, so that converter flow valve130 connects the trim system 60, 80 to the pump clutch feed 25 tothereby control the engagement and disengagement of the pump clutch 21.

If the vehicle is not in one of stages I, II or III, or if analysis ofsome other vehicle parameter indicates that a second coupler needs to becontrolled, then at functional block 220 the first actuator will be setto a second state such that the second coupler will be controlled by thetrim system. For example, in the illustrative embodiment, if the vehicleis in stage IV or V, then valve 180 will be activated or set to the onposition, so that converter flow valve 130 connects the trim system 60,80 to the lockup clutch feed 29 to thereby control the engagement anddisengagement of the lockup clutch 23.

At functional block 222, electrical signals are sent to the trim systemas needed to control operation of the trim system as it relates to theselected clutch that is currently under control. In the illustrativeembodiment, if the pump clutch 21 is being controlled, appropriateelectrical signals will be sent to the actuator 60 according to thestage of torque converter operation or other factors. For example, ifthe torque converter 15 is in the idle stage, an electrical signal willbe sent to actuator 60 thereby causing fluid pressure to be applied tovalve head 118, resulting in disengagement of the pump clutch 21.Appropriate electrical signals are likewise sent to actuator 60 tocontrol the lockup clutch 23 when valve 130 has been moved to thepressure set position.

The present disclosure describes patentable subject matter withreference to certain illustrative embodiments. The drawings are providedto facilitate understanding of the disclosure, and may depict a limitednumber of elements for ease of explanation. Except as may be otherwisenoted in this disclosure, no limits on the scope of patentable subjectmatter are intended to be implied by the drawings. Variations,alternatives, and modifications to the illustrated embodiments may beincluded in the scope of protection available for the patentable subjectmatter.

1. An electronic control for a torque converter of a vehicle having aplurality of operational phases, the torque converter having selectivelyand independently engageable clutches including a pump clutch and atorque converter clutch, the electrical control comprising circuitry togenerate control signals to: disengage the pump clutch during an idlephase; disengage the torque converter clutch during the idle phase;engage the pump clutch during a launch phase; disengage the torqueconverter clutch during the launch phase; engage the pump clutch duringa lockup phase; and engage the torque converter clutch during the lockupphase.
 2. The electronic control of claim 1, wherein the electroniccontrol applies a closed loop control method to the torque converterincluding one or more of: a reduced engine load at stop (RELS) method, avariable K factor method, and an electronic converter clutch control(ECCC) method.
 3. The electronic control of claim 2, wherein theelectronic control applies the variable k factor control method tocontrol the pump clutch during the launch phase.
 4. The electroniccontrol of claim 1, wherein the control signals cause a transmissioncoupled to the torque converter to assume a lower gear ratio in responseto a request for motion during the launch phase.
 5. The electroniccontrol of claim 1, wherein the control signals cause engagement of thepump clutch and disengagement of the torque converter clutch during atorque converter phase.
 6. The electronic control of claim 5, whereinthe control signals cause a constant pressure to be maintained in atorus cavity of the torque converter during the torque converter phase.7. The electronic control of claim 1, wherein the control signals causeengagement of the pump clutch and cause the torque converter clutch tobe trimmed during a torque converter clutch trim phase.
 8. Theelectronic control of claim 1, wherein the electronic control appliesthe ECCC control method to the torque converter clutch during the lockupphase.
 9. The electronic control of claim 1, wherein the control signalscause the pump clutch to be trimmed during the launch phase trim phase.10. The electronic control of claim 1, wherein when the control signalscause the pump clutch to engage, the controls signals cause the pumpclutch to at least partially engage.
 11. The electronic control of claim1, wherein when the control signals cause the torque converter clutch toengage, the controls signals cause the torque converter clutch to atleast partially engage.
 12. An electronic control to control a torqueconverter of a vehicle having a plurality of operational phases, thetorque converter having selectively and independently engageableclutches including a pump clutch and a torque converter clutch, theelectrical control comprising circuitry to generate control signals to:monitor a vehicle state indicator; determine, from the vehicle stateindicator, a current operational phase of the vehicle; control the pumpclutch if the current operational phase is a first operational phase;and control the torque converter clutch if the current operational phaseis a second operational phase different from the first operationalphase.
 13. The electronic control of claim 12, wherein the controlsignals cause a trim system to be fluidly connected to the pump clutchif the current operational phase is the first operational phase.
 14. Theelectronic control of claim 12, wherein the control signals set anactuator to a first state to cause a converter flow valve to fluidlyconnect the trim system to the pump clutch.
 15. The electronic controlof claim 13, wherein the control signals cause the torque converterclutch to be fluidly connected to a trim system if the currentoperational phase is the second operational phase.
 16. The electroniccontrol of claim 13, wherein the control signals set an actuator to asecond state to cause a converter flow valve to fluidly connect the trimsystem to the torque converter clutch.
 17. A method for controlling apump clutch and a torque converter clutch of a torque converter of avehicle having a plurality of operational phases, the method comprising:monitoring a vehicle state indicator; determining, from the vehiclestate indicator, a current operational phase of the vehicle; controllingthe pump clutch if the current operational phase is a first operationalphase; and controlling the torque converter clutch if the currentoperational phase is a second operational phase different from the firstoperational phase.
 18. The method of claim 17, comprising monitoring aplurality of vehicle state indicators indicating a current status of acomponent of the vehicle.
 19. The method of claim 17, comprisingcontrolling a converter flow valve to selectively control the pumpclutch and the torque converter clutch.
 20. The method of claim 19,comprising sending electrical signals to an actuator to control theconverter flow valve to cause the converter flow valve to selectivelyfluidly couple the pump clutch and the torque converter clutch to a trimsystem.
 21. The method of claim 20, comprising sending electricalsignals to the trim system to control operation of the trim system whenthe trim system is selectively fluidly coupled to the pump clutch andthe torque converter clutch.